1. Field of the Invention
This invention relates generally to a method and apparatus for detecting the occurrence of amplitude compression in receivers, and more particularly to a method and apparatus for detecting the occurrence of pulse compression in the receivers and pulse processors of aircraft guidance systems of the type that compare the amplitudes of received pulses to provide guidance information.
2. Background of the Invention
Approach guidance systems typically utilize a radio transmitter that alternately transmits pulses in overlapping beams. Such systems typically have two horizontally overlapping beams and two vertically overlapping beams to provide azimuth and elevation guidance information. A receiver in the aircraft receives the signals from the overlapping beams and compares the amplitudes of the pulses received from the various beams. When the pulses received from the left and right beams are equal in amplitude the aircraft is on the correct azimuth, and when the amplitudes of the pulses received from the up and down lobes of the elevation system are equal, the aircraft is on the correct glide slope.
While the above described system provides satisfactory operation under most circumstances, certain failures in the pulse receiving and processing circuitry aboard the aircraft can cause compression of pulses received from one of the beams relative to the others, and thus provide an erroneous reading to the pilot which could place the aircraft off course and result in a hazardous situation.